DYNAMIC ANALYSIS OF UPGRADED DRAFT GEAR IN FREIGHT WAGON

Abstract

The work focuses on developing mathematical model for predicting the longitudinal dynamics of a freight train consist. The work is more centred on the dynamic analysis of upgraded draft gear (Miner RF-36 1 of Indian Railways) for a given freight wagon consist. The analysis involves simulation of a freight train consist equipped with draft gear as a coupler system. A formulation of train and wagon connection model is worked out for two freight wagons and locomotive. The entire system is modelled as a multi-degree mass-spring-damper system and subjected to forces which would simulate the actual working condition. In the initial phase of the modelling, the springs and dampers are considered to behave linearly. In the latter part, geometric and material nonlinearity of the draft gear system is introduced in the model as nonlinear spring. l-lowever, the damper was considered to be linear in the entire work. A numerical integration scheme was utilized to determine dynamic behaviour of each mass, i.e. wagon as well as draft gear. Fast Fourier transform was used to determine the dominating frequencies from the acceleration response of draft gear. Time domain response for displacements, velocities and accelerations, as well as phase plane trajectories have been used to analyse to dynamics of the train consist for various scenarios. Twelve such cases have been simulated by varying the speed and load of the freight wagons. It is seen that as a linear system, the freight train consist under unloaded and loaded condition behaved linearly at all speeds. Phase trajectory showed a closed loop phenomenon with multi periodic orbit. For the nonlinear freight train model chaotic behaviour was observed. As simulation was performed for higher speed nonlinear behaviour was noticeably increasing. Phase trajectories showed a strange attractor at the center point. Thus modelling and analysis of draft gear as a separate mass gave explicit behaviour of the draft gear arrangement and revealed everything from mode shapes to linear and nonlinear response of the freight wagon system.